You most certainly need an amplifier. Passive speakers do not run without an amplifier.....
– ScottFSep 2 '16 at 18:40

Thanks for the answers, I really don't get why this was closed. Other questions about that microphone brand is not working on that os version or using that sound card to record this stuff are still opened... but ok whatever.
– PaoloOct 8 '16 at 11:41

(@Paolo) ...FYI Most studios use active monitors for various reasons. Most professional interfaces will have 6.3mm(1/4in) TRS(balllanced) line outputs with a +4dBu(professional) level.
– Marc WSep 2 '16 at 13:20